1. Field of the Invention
The present invention relates to a non-contact type transmission device for use in an information recording apparatus, e.g., a video tape recorder and to a rotary magnetic head unit having the non-contact type transmission device.
2. Description of the Related Art
Video tape recorders, tape streamers and so on are known as apparatuses for recording information on a magnetic tape and for reproducing information from the magnetic tape. An information recording apparatus of this kind has a rotary magnetic head unit for a recording signal on a magnetic tape and for reproducing a signal recorded on a magnetic tape.
The rotary magnetic head unit has a rotating drum and a fixed drum. The rotating drum has a recording head and a reproducing head. The recording head is a head for recording a signal on a magnetic tape, and the reproducing head is used to reproduce a signal recorded on a magnetic tape.
The rotating drum holds the recording head and the reproducing head and rotates relative to the fixed drum by the operation of a motor to scan a magnetic tape with the recording head or the reproducing head by, for example, the helical scanning method, thereby recording information on the magnetic tape or reproducing information from the magnetic head.
If such a helical scanning system is used, signals can be recorded on a magnetic tape at a high density and the relative speed between the magnetic tape and the magnetic head can be increased.
The helical scanning type rotary magnetic head unit needs to transmit signals and electric power between the rotating drum and the fixed drum in a non-contact manner since the recording head and the reproducing head are accommodated in the rotating drum. For example, there is a need to transmit a reproduction signal, which is obtained by the reproducing head, from the rotating drum side to the fixed drum side in a non-contact manner, and to supply electric power from the fixed drum side to a circuit board provided on the rotating drum side.
Conventional rotary magnetic head units of this kind use a rotary transformer for a non-contact signal transmission system only and require another rotary transformer for power supply if non-contact power supply is necessary. A signal system rotary transformer and a power supply rotary transformer are separately provided in such conventional magnetic head units in order to prevent crosstalk of a transmitted signal used with the power supply rotary transformer to the signal system rotary transformer.
This xe2x80x9ccrosstalkxe2x80x9d is a leak of a signal through a leakage magnetic field between adjacent signal and power supply systems or between different signal systems.
Rotary magnetic head units having two rotary transformers, however, are large in size and high in manufacturing cost. Also, it is technically difficult to incorporate two rotary transformers in a small rotary magnetic head unit.
A magnetoresistive element head (MR head) is used as a head for reproducing information recorded on a magnetic recording medium. A reproducing magnetoresistive element head constantly requires a bias current when operated to obtain a reproduction signal. A magnetoresistive element head is a head in which a change in resistance is caused by a change in magnetic field, and in which a change in signal magnetic field (input signal) is converted into a change in resistance to be extracted as a change in reproduction output signal.
Such a magnetoresistive element head can be used advantageously as a reproducing head because of its ability to obtain a stable reproduction output signal independent of the magnetic tape speed.
In using a reproducing magnetoresistive element head of this kind by causing a bias current to flow continuously therethrough during reproduction, there is a problem relating to wear of the magnetoresistive element head. That is, as the total of time periods through which a magnetoresistive element head is operated to reproduce signals from magnetic tapes, the amount of wear of the head increases inevitably. With wear of the head, a change occurs in signal reproduction characteristics of the magnetoresistive element head. A suitable reproduction output signal cannot be obtained unless the bias current is changed according to wear of the head.
In view of the above-described circumstances, an object of the present invention is to provide a non-contact type transmission device in which both non-contact transmission in a signal system and non-contact transmission of power supply can be reliably performed, and which can be reduced in size, and a rotary magnetic head unit having the non-contact type transmission device.
Another object of the present invention is to provide a rotary magnetic head unit in which, in using a reproducing magnetic head formed of a magnetoresistive element, the bias current for the head can be controlled according to wear of the head so as to optimize a reproduction signal output from the reproducing head.
To achieve the above-described objects, according to the present invention, there is provided a non-contact type transmission device for transmitting a power supply and a signal between a rotating member and a fixed member in a non-contact manner, the transmission device comprising the rotating member having a rotating member power supply wiring section for transmitting a power supply, a rotating member signal wiring section for transmitting a signal, and at least one rotating member crosstalk prevention section for preventing crosstalk between the rotating member power supply wiring section and the rotating member signal wiring section, the rotating member crosstalk prevention section being positioned between the rotating member power supply wiring section and the rotating member signal wiring section, and the fixed member having a fixed member power supply wiring section for transmitting a power supply between itself and the rotating member power supply wiring section, a fixed member signal wiring section for transmitting a signal between itself and the rotating member signal wiring section, and at least one fixed member crosstalk prevention section for preventing crosstalk between the fixed member power supply wiring section and the fixed member signal wiring section, the fixed member crosstalk prevention section being positioned between the fixed member power supply wiring section and the fixed member signal wiring section.
In the transmission device in accordance with the present invention, on the rotating member side, the rotating member crosstalk prevention section is positioned between the rotating member power supply wiring section and the rotating member signal wiring section to prevent crosstalk between these two sections. Similarly, on the fixed member side, the fixed member crosstalk prevention section is positioned between the fixed member power supply wiring section and the fixed member signal wiring section to prevent crosstalk between these sections.
If one non-contact type transmission device thus arranged is used, power supply transmission and signal transmission can be performed simultaneously while power supply-signal crosstalk is prevented or reduced. The non-contact transmission device can therefore be designed so as to be smaller in size.
According to the present invention, the rotating member and the fixed member are disk-like members opposed to each other or cylindrical members coaxial with each other.
Preferably, according to the present invention, a plurality of rotating member crosstalk prevention sections are provided on the rotating member side, and, correspondingly, a plurality of fixed member cross-talk prevention sections are provided on the fixed member side, thereby preventing crosstalk more reliably.
According to another aspect of the present invention, there is provided a rotary magnetic head unit for recording a signal on an information recording medium in the form of a tape and for reproducing a signal from the information recording medium, the rotary magnetic head unit comprising a non-contact type transmission device having a rotating member and a fixed member and capable of transmitting a power supply and a signal between the rotating member and the fixed member in a non-contact manner, a rotating drum on which the rotating member of the transmission device is supported, a fixed drum on which the fixed member of the transmission device is supported, the rotating member of the transmission device having a rotating member power supply wiring section for transmitting a power supply, a rotating member signal wiring section for transmitting a signal, and at least one rotating member crosstalk prevention section for preventing crosstalk between the rotating member power supply wiring section and the rotating member signal wiring section, the rotating member crosstalk prevention section being positioned between the rotating member power supply wiring section and the rotating member signal wiring section, and the fixed member of the transmission device having a fixed member power supply wiring section for transmitting a power supply between itself and the rotating member power supply wiring section, a fixed member signal wiring section for transmitting a signal between itself and the rotating member signal wiring section, and at least one fixed member crosstalk prevention section for preventing crosstalk between the fixed member power supply wiring section and the fixed member signal wiring section, the fixed member crosstalk prevention section being positioned between the fixed member power supply wiring section and the fixed member signal wiring section.
In the rotary magnetic head unit having the rotating and fixed drums in accordance with the present invention, on the rotating member side in the transmission device, the rotating member crosstalk prevention section is positioned between the rotating member power supply wiring section and the rotating member signal wiring section to prevent crosstalk between these two sections. Similarly, on the fixed member side, the fixed member crosstalk prevention section is positioned between the fixed member power supply wiring section and the fixed member signal wiring section to prevent crosstalk between these two sections.
If one non-contact type transmission device thus arranged is used, power supply transmission and signal transmission can be performed simultaneously while power supply-signal crosstalk is prevented or reduced. The non-contact transmission device can therefore be designed so as to be smaller in size.
According to the present invention, the rotating member and the fixed member are disk-like members opposed to each other or cylindrical members coaxial with each other.
Preferably, according to the present invention, a plurality of rotating member crosstalk prevention sections are provided on the rotating member side, and, correspondingly, a plurality of fixed member crosstalk prevention sections are provided on the fixed member side, thereby preventing crosstalk more reliably.
Preferably, the transmitted signal comprises a recording signal supplied to a recording head and a reproduction signal obtained by a reproducing head, and the power supply is used for amplification of the reproduction signal obtained by the reproducing head, thus enabling amplification of the reproduction signal from the reproducing head in the rotating drum.
According to the present invention, the operation of an external oscillator for producing the power supply is stopped when the recording head is in contact with the information recording medium, thereby preventing crosstalk to the recording head operating for recording.
Also, according to the present invention, a maximum frequency band of an alternating current from the external oscillator for the power supply is set different from the frequency band of the signals, thereby prevent crosstalk from the power supply side to the signal side.
Preferably, according to the present invention, the rotating member signal wiring section is connected directly to the recording head. The impedance of the recording signal system in a low frequency range is thereby reduced, so that the recording head and the rotary signal wiring section can function substantially as a short-circuit ring forming a crosstalk prevention section when a signal is reproduced with the reproducing head, thereby reducing crosstalk from the power supply side to the reproducing head. Also, the crosstalk prevention effect can be further improved by short-circuiting a subsection of the fixed member wiring section constituting the recording system at the time of reproduction
Preferably, according to the present invention, the rotating member crosstalk prevention section is placed between a subsection of the rotating member signal wiring section for transmitting a recording signal and the rotating member power supply wiring section while the fixed member crosstalk prevention section is placed between the subsection of the fixed member signal wiring section for transmitting a recording signal and the fixed member power supply wiring section, thereby reliably preventing or reducing crosstalk between the signal wiring sections and the power supply wiring sections.
According to still another aspect of the present invention, there is provided a rotary magnetic head unit for recording a signal on an information recording medium in the form of a tape and for reproducing a signal from the information recording medium, the rotary magnetic head unit comprising a transmission device having a rotating member and a fixed member and capable of transmitting a power supply and signals between the rotating member and the fixed member in a non-contact manner, a plurality of recording heads for recording signals, at least one reproducing head for reproducing signals, a rotating drum on which the plurality of recording heads and the reproducing head are disposed, and on which the rotating member of the transmission device is supported, a fixed drum on which the fixed member of the transmission device is supported, the rotating member of the transmission device having a rotating member power supply wiring section for transmitting a power supply, a rotating member signal wiring section for transmitting signals, and at least one rotating member crosstalk prevention section for preventing crosstalk between the rotating member power supply wiring section and the rotating member signal wiring section, the rotating member crosstalk prevention section being positioned between the rotating member power supply wiring section and the rotating member signal wiring section, and the fixed member of the transmission device having a fixed member power supply wiring section for transmitting a power supply between itself and the rotating member power supply wiring section, a fixed member signal wiring section for transmitting signals between itself and the rotating member signal wiring section, and at least one fixed member crosstalk prevention section for preventing crosstalk between the fixed member power supply wiring section and the fixed member signal wiring section, the fixed member crosstalk prevention section being positioned between the fixed member power supply wiring section and the fixed member signal wiring section, wherein a subsection of the rotating member signal wiring section relating to a recording signal recorded by each of the recording heads is placed between the rotating member power supply wiring section and a subsection of the rotating member signal wiring section relating to a reproduction signal obtained by the reproducing head, and a subsection of the fixed member signal wiring section relating to a recording signal recorded by each of the recording heads is placed between the fixed member power supply wiring section and a subsection of the fixed member signal wiring section relating to a reproduction signal obtained by the reproducing head.
In this rotary magnetic head unit of the present invention, the plurality of recording heads for recording signals and the reproducing head for reproducing signals are disposed on the rotating drum, and the subsection of the rotating member signal wiring section relating to a recording signal supplied to each of the recording heads is placed between the rotating member power supply wiring section and the subsection of the rotating member signal wiring section relating to a reproduction signal from the reproducing head while the subsection of the fixed member signal wiring section relating to a recording signal supplied to each of the recording heads is placed between the fixed member power supply wiring section and the subsection of the fixed member signal wiring section relating to a reproduction signal from the reproducing head.
The rotating member crosstalk prevention section and the fixed member crosstalk prevention section, the rotating member signal wiring section relating to a recording signal supplied to each recording head and the fixed member signal wiring section relating to a recording signal supplied to each recording head serve to prevent occurrence of crosstalk between the rotating member power supply wiring section and the rotating member signal wiring section and occurrence of crosstalk between the fixed member power supply wiring section and the fixed member signal wiring section.
According to a further aspect of the present invention, there is provided a rotary magnetic head unit for recording a signal on an information recording medium in the form of a tape and for reproducing a signal from the information recording medium, the rotary magnetic head unit comprising a transmission device having a rotating member and a fixed member and capable of transmitting a power supply and signals between the rotating member and the fixed member in a non-contact manner, a plurality of recording heads for recording signals, at least one reproducing head for reproducing signals, a rotating drum on which the plurality of recording heads and the reproducing head are disposed, and on which the rotating member of the transmission device is supported, a fixed drum on which the fixed member of the transmission device is supported, the rotating member of the transmission device having a rotating member power supply wiring section for transmitting a power supply, and a rotating member signal wiring section for transmitting signals, and the fixed member of the transmission device having a fixed member power supply wiring section for transmitting a power supply between itself and the rotating member power supply wiring section, and a fixed member signal wiring section for transmitting a signal between itself and the rotating member signal wiring section, wherein a subsection of the fixed member signal wiring section relating to a recording signal recorded by each of the recording heads is placed between the fixed member power supply wiring section and a subsection of the fixed member signal wiring section relating to a reproduction signal obtained by the reproducing head.
In this rotary magnetic head unit of the present invention, the plurality of recording heads for recording signals and the reproducing head for reproducing signals are disposed on the rotating drum, and the subsection of the rotating member signal wiring section relating to a recording signal supplied to each of the recording heads is placed between the rotating member power supply wiring section and the subsection of the rotating member signal wiring section relating to a reproduction signal from the reproducing head while the subsection of the fixed member signal wiring section relating to a recording signal supplied to each of the recording heads is placed between the fixed member power supply wiring section and the subsection of the fixed member signal wiring section relating to a reproduction signal from the reproducing head.
The rotating member signal wiring section relating to a recording signal supplied to each recording head and the fixed member signal wiring section relating to a recording signal supplied to each recording head serve to prevent occurrence of crosstalk between the rotating member power supply wiring section and the rotating member signal wiring section and occurrence of crosstalk between the fixed member power supply wiring section and the fixed member signal wiring section.
According to still a further aspect of the present invention, there is provided a rotary magnetic head unit comprising a transmission device having a rotating member and a fixed member and capable of transmitting a power supply and a signal between the rotating member and the fixed member in a non-contact manner, a rotating drum on which the rotating member of the transmission device is supported, a fixed drum on which the fixed member of the transmission device is supported, a reproducing head for reproducing a signal recorded on a magnetic tape, the reproducing head being formed of a magnetoresistive element and supported on the rotating drum, the rotating member of the transmission device having a rotating member power supply wiring section for transmitting a power supply, and a rotating member reproduction signal wiring section for transmitting a reproduction signal obtained by the reproducing head, the fixed member of the transmission device having a fixed member power supply wiring section for transmitting a power supply between itself and the rotating member power supply wiring section, and a fixed member reproduction signal wiring section for transmitting a signal between itself and the rotating member reproduction signal wiring section, and bias current control means for changing a bias current which is supplied to the reproducing head during reproduction, and which is produced from a power supply transmitted by the rotating member power supply wiring section and the fixed member power supply wiring section, the bias current control means changing the bias current according to the amount of wear of the reproducing head during a time period through which magnetic tape signals are reproduced with the reproducing head.
In this rotary magnetic head unit of the present invention, a power supply used in the rotary drum can be transmitted between the rotating member power supply wiring section in the rotating member and the fixed member power supply wiring section in the fixed member, and a reproduction signal obtained by the reproducing head is transmitted between the rotating member reproduction signal wiring section in the rotating member and the fixed member reproduction signal wiring section in the fixed member.
From the power supply transmitted between the rotating member power supply wiring section and the fixed member power supply wiring section, the bias current to be supplied to the reproducing head formed of a magnetoresistive element on the rotating drum is obtained, thereby enabling the reproducing head to reproduce signals from the magnetic tape.
During reproduction, the bias current control means changes the bias current supplied to the reproducing head according to the amount of wear of the reproducing head, thereby making it possible to obtain the magnetic tape reproduction output signal in an optimum state no matter what the amount of wear of the reproducing head.